There has been a technique of three-dimensionally shaping a resin packaging member used for a flexible container such as a pouch. For instance, a pouch surface is embossed to have a character (here, this term may indicate also “letter” or “numeral”), a figure, a sign or the like, or decorated three-dimensionally to have a character, a mark or the like, thereby improving the design.
The following methods for embossing or shaping a three-dimensional decoration on a pouch have been proposed. Patent document 1 proposes a method for shaping a predetermined embossed pattern by heating and/or cooling a predetermined site of a bag-like container and by pressing with a pair of molds consisting of a male mold and a female mold. Patent document 2 proposes a processing method for shaping a protruded portion on a laminate film. According to Patent document 2, a mold for a character or a mark is heated and pressed onto a laminate film including a plurality of films different from each other in the thermal expansion coefficients, so that a part of the laminate film is heated to have a shape of the heated mold, and later, the heated mold is separated from the laminate film to stop the heating. In this manner, the shape of the heated mold may be transferred as a swelling to the film with a smaller thermal expansion coefficient and the laminate film may have a protruded portion.
However, according to the shaping method of Patent document 1, the temperature is raised to be substantially equivalent to or a little lower than the melting point of polyethylene arranged on the inner surface of the bag-like container, specifically to about 110° C. According to the processing method of Patent document 2, the temperature is raised to a range of about 100 to about 130° C. and the heating time is about 0.5 to about 5 seconds when the film with a large thermal expansion coefficient is made of a polyethylene-based resin, for instance. That is, in any case of Patent documents 1 and 2, the components are heated to a relatively high temperature approximate to the melting points of the films. This may cause some disadvantages. For instance, the resin flows during compression shaping, which inhibits reliable formation of a well-defined embossed pattern or a protruded portion. This may also cause excessive decrease in film thickness, cracks, and rupture at the periphery of the embossed pattern or the protruded portion. As a result, it may be difficult to obtain basic functions such as a gas barrier property, a vapor barrier property, a drop impact resistance, and a piercing resistance.
For solving these problems, the present inventors have proposed a three-dimensionally shaping method to compress-shape a laminated synthetic resin film in the thickness direction in a cold process, where the film comprises at least an innermost soft inner film and a high-strength outer film arranged outside (Patent document 3). In this method, there is no necessity of heating or cooling, and thus, energy required for processing can be reduced remarkably, and at the same time, the processing time can be shortened to enable a high-speed processing. In other words, the method is excellent also from the viewpoint of productivity.